Amount Of Ce Doping Research Articles

Optical Properties of Ce-Doped ZnO Nanowires Directionally Grown by Hydrothermal Method

Well directionally grown Ce-doped ZnO nanowires were successfully synthesized by a simple hydrothermal method. The Ce dopant plays a key role in evolving the morphology, affecting the crystalline size, and forming the uniform nanostructure of the ZnO nanowires. The amount of Ce dopant in the ZnO nanowires also affects the regions of blue-shift in the UV and green emission peaks and the intensities of emission peaks based on the cathodoluminescence spectra of the nanowires. Moreover, the effect of Ce doping amount on the microstructure of the nanowires is also presented.

Electrical properties of Pt/Bi3.25La0.75Ti3O12/Pt thin film capacitors tailored by cerium doping

Cerium-doped Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated by depositing sol-gel solutions on Pt/Ti/SiO2/Si 〈100〉 substrates. The Ce-doping in BLT up to 6.7% of Ti atoms did not affect the single-phase bismuth-layered structure but small modification was observed in structural orientation, which influenced the microstructure and ferroelectric properties of BLT films. As we did not observe any structural distortion in x-ray diffraction data, it was suggested that doped Ce4+ was converted to Ce3+ during the annealing at 750 °C, and cerium ions might be substituted at Bi-site in BLT films. The small amount of Ce doping (1% of Ti atoms) enhanced the remanent polarization and reduced the coercive field by about 17% in BLT films, and these films showed fatigue-free response up to 1010 switching cycles at 300 kV/cm applied fields. Moderately Ce-doped films (1.7% of Ti atoms) also showed fatigue-free response up to 1010 switching cycles in 200 kV/cm applied field, but the polarization was found to increase with switching cycles when applied field was higher than 200 kV/cm. After Ce doping, the oxygen vacancy concentration may decrease in BLT films, and consequently, one can expect less domain pinning and higher fatigue resistance. Under the high cycling field, the high probability of field-assisted unpinning may be the main cause for the increased polarization.

Evaluation of properties of YAG (Ce) ceramic scintillators

We measured basic properties of three ceramic Y/sub 3/Al/sub 5/O/sub 12/ (YAG) scintillators doped with Ce to a concentration of 0.5, 0.05, and 0.005 mol%, in comparison with a monocrystalline YAG scintillator with unknown amount of Ce doping. First, optical transparency and emission spectra were investigated. We confirmed that the transparency of the ceramics is comparable to that of the monocrystalline one (/spl sim/80%) in wavelengths longer than /spl sim/500 nm. The ceramics did not show an indication of lattice defects which is present in the monocrystalline YAG. Then the response to /spl gamma/-rays was studied using a phototube as a scintillation light detector. The 0.5 mol% sample exhibited the highest light yield (/spl sim/40% of CsI), with an energy resolution of about 7.2% at /sup 137/Cs 662 keV photoabsorption peak. The optimum Ce concentration for a /spl sim/2 mm thick ceramic YAG was determined to be /spl sim/0.1 mol%. Using the delayed coincidence method, the principal time constant of the ceramic YAGs was measured as /spl sim/80 ns. By irradiating 5.49 MeV /spl alpha/-particles, the /spl alpha/-ray to /spl gamma/-ray light yield ratio of the ceramic YAGs was found to depend negatively on the amount of Ce; namely, 0.28, 0.20, and 0.13 in the increasing order of the Ce concentration. The 200-1000 keV intrinsic background of the 0.5 mol% ceramic was /spl sim/10/sup -5/ counts/s/cm/sup 3/, indicating that it is not significantly contaminated by radioactive impurities.

Ferroelectric relaxor Ba(Ti,Ce)O3

The dielectric behaviour of Ba(Ti1−yCey)O3 solid solutions (y = 0–0.3)has been studied. A small amount of Ce doping (y = 0.02)has weak influence on the dielectric behaviour of Ba(Ti1−yCey)O3. With increasingCe concentration, three phase transitions of pure BaTiO3 are pinched into onerounded dielectric peak with frequency dispersion, and the relaxationtime follows the Vogel–Fulcher relation. The evolution from a normalferroelectric to a ferroelectric relaxor is emphasized. High strains (S = ∼ 0.1–0.19%)with a small hysteresis under ac fields are obtained in ferroelectric relaxorsBa(Ti1−yCey)O3. The physical mechanism of the relaxation process, the pinchingeffect of the phase transitions and their influence on the ferroelectric andelectrostrictive behaviour are discussed.